1. Technical Field
The present invention relates to a semiconductor device having an underfill filled in a gap between a semiconductor chip and a substrate, and a method of manufacturing the same.
2. Related Art
There has been known a conventional printed wiring board described in Japanese Laid-Open Patent Publication No. 2006-93493. The publication describes a printed wiring board having an insulating substrate provided with a protective layer roughened on the surface thereof using a buff or wet blasting, and an insulating base (prepreg) stacked on the protective layer. A film composed of epoxy acrylate resin is used for the protective layer.
The publication describes that such configuration can improve adhesiveness between the protective layer and the insulating base.
Japanese Laid-Open Patent Publication No. H6-97634 describes a printed wiring board having a substrate provided with mounting pads, and a solder resist composed of a dry film and having openings allowing the top surface of the mounting pads to expose therein.
Paragraphs below will explain subjects to be solved by the present invention, referring to FIGS. 4A, 4B and 5 showing a method of manufacturing a semiconductor device.
First, as shown in FIG. 4A, a solder resist film 116 is formed by coating a negative-type liquid solder resist on a substrate 112 having first mounting pads 114 preliminarily formed thereon, and patterning the coated film by photographic development so as to form openings 115.
Next, the solder resist film 116 is subjected to desmearing using a permanganate salt and plasma treatment, so as to achieve a surface roughness Ra (arithmetical mean roughness) of 0.05 μm or larger, to thereby obtain a roughened solder resist film 118 as shown in FIG. 4B.
Then, as shown in FIG. 5A, pretinnings 120 are formed on the first mounting pads 114 on the substrate 112, to thereby obtain a printed wiring board.
Next, as shown in FIG. 5B, mounting pads 128 on the side of a semiconductor chip 126 and the first mounting pads 114 on the substrate 112 side are connected while placing solder bumps 122 in between, to thereby electrically connect the semiconductor chip 126 and the printed wiring board with each other. An underfill material is then filled between the semiconductor chip 126 and the solder resist film 118 so as to form an underfill film 124, to thereby obtain a semiconductor device.
Thus-obtained semiconductor device had, however, still some room for improvement in uniformity of wettability of the solder resist film 118. For this reason, cleanability of the surface of the solder resist film 118 after flip-chip mounting was sometimes insufficient, while leaving residue such as flux on the surface of the solder resist film 118. Bubbles were sometimes produced at the interface between the underfill film 124 and the solder resist film 11. These residue and bubbles were sometimes causative of producing voids in the underfill film 124, and sometimes resulted in inter-bump short circuiting.
In addition, the underfill material sometimes ran out from the gap between the semiconductor chip 126 and the solder resist film 118 in the process of filling, which could inhibit uniform formation of an underfill fillet, could cause bleeding, and could degrade yield of the semiconductor device.
The present invention was conceived after considering the above-described situation, wherein subjects of which reside in providing a semiconductor device suppressed in the inter-bump short circuiting, and a method of manufacturing the same excellent in the yield of product.